Frequency-hopping (FH) communications are a spread spectrum method of transmitting radio signals. In general, frequency hopping involves rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. It is typically utilized as a multiple access method in the frequency-hopping code division multiple access (FH-CDMA) scheme.
Spread-spectrum transmission techniques, including FH techniques, typically provide numerous advantages over fixed-frequency transmission techniques. First, spread-spectrum signals are generally highly resistant to narrowband interference. The process of re-collecting a spread signal typically spreads out the interfering signal, causing it to recede into the background. Second, spread-spectrum signals are typically difficult to intercept. In general, a spread spectrum signal, such as an FH signal, appears as an increase in the background noise to a narrowband receiver. As a result, a potential eavesdropper would only be able to intercept the transmission if they knew the pseudorandom sequence. Third, spread-spectrum transmissions can generally be configured to share a frequency band with many types of conventional transmissions with minimal interference. The spread-spectrum signals typically add minimal noise to the narrow-frequency communications, and vice versa. As a result, bandwidth can be utilized more efficiently.
However, spread spectrum communications, including FH spread spectrum communications are still susceptible to emissions from collocated radio frequency emitters. In the case of critical mission communications, such as in military or public safety communications, this can result in loss or corruption of information during reception.